1. Field Of The Invention
This invention is related to a personal dosimeter for registering gaseous contaminants in the atmosphere. More particularly, it is related to a dosimeter for detecting formaldehyde wherein a sodium bisulfite absorbant medium is modified with sodium bicarbonate.
2. Description Of The Prior Art
In response to the increasing concern about the health of workers who are exposed to harmful pollutants in the air, it has become necessary to monitor the concentration of the air-borne contaminants. One development for this purpose involved a rather large air pump which would force air to be sampled through a filter, trapping particulate contaminants. This obviously is unavailing for the monitoring of gaseous contaminants and, even for particles, is not accurate for determining the concentration of the particles in the sampled atmosphere.
Personal sampling devices which are worn by individual workers and which passively collect the contaminants have also been used. For example, a device which utilized the molecular diffusion of the gas to be monitored to collect the sample has been described in the American Industrial Hygiene Association Journal, Volume 34, pages 78-81 (1973). This device and others like it, called impinging tubes, are often cumbersome to use since their designs and delicate constructions necessitate that they always be oriented properly to sample accurately the atmosphere and to prevent dislocation of the sampling mechanism within the tube.
The need arose for the development of personal dosimeters that simply but accurately collected gaseous contaminants in proportion to their average atmospheric concentration. Examples of dosimeters designed for colorimetric analysis are disclosed in Kring U.S. Pat. No. 4,208,371 issued June 17, 1980; Kring et al. U.S. Pat. No. 4,235,097 issued Nov. 25, 1980; and Kring U.S. Pat. No. 4,269,804 issued May 26, 1981. The color intensity of the exposed collecting medium in those dosimeters is proportional to the dose-level of gas sampled. The color stability of suitable collecting mediums, however, is affected by several variables including storage life.
A need became apparent for the availability of a more stable absorbant medium, particularly for dosimeters used in the detection of formaldehyde.